Poly(n-butyl methacrylate-co-pentaerythritolriacrylate) (poly(n-BMA-co-PETA)) gel was first synthesized via reversible-deactivation radical polymerization (RDRP) technique with Cu(0)/N,N,N',N'-tetramethylethylenediamine (TEMED) as catalyst system, 2-cyanoprop-2-yl-1-dithionaphthalate (CPDN) as chain transfer agent, and N,N-dimethylformamide (DMF) as solvent. The results exhibited well-controlled characters of the new RDRP technique. The poly(n-BMA-co-PETA) gel exhibited preferable three-dimensional network cross-linked structure. It possessed high oil absorption capacity and perfect reusability. The maximum oil absorption capacity was 52.6 g/g. The gel may have a number of potential applications in controlling oil pollution. The influence factors on oil absorbency were discussed in detail as well.